San Francisco billionaire Tom Steyer has spent a staggering $76 million to promote climate change as a political issue in this year’s elections, but the subject isn’t exactly firing up the electorate.

Polls show voters continue to rank climate change at the bottom of their priority lists. Even in races featuring the “Steyer Seven,” the Democratic candidates selected by Mr. Steyer as the chief beneficiaries of his largesse, the issue is barely registering on the campaign trail.

Take the Senate race in New Hampshire. NextGen Climate Action, Mr. Steyer’s political action committee, has invested heavily in television advertising and the ground game on behalf of Sen. Jeanne Shaheen, a Democrat, in her re-election bid against Republican Scott Brown.

What impact has climate change had on the contest? “None,” said Andrew Smith, director of the University of New Hampshire Survey Center.

“It’s not been an issue candidates have been talking about the in the Senate race. It’s not in the kinds of questions that come up in the debates, and it’s certainly not one of the issues voters have told us are important or a serious problem,” Mr. Smith said.

Same with the Senate race in Michigan, where NextGen is supporting Rep. Gary C. Peters in his race against Republican Terri Lynn Land, a former Michigan secretary of state.

“There hasn’t really been a peep about it,” said political analyst Bill Ballenger, founder of Inside Michigan Politics. “I’ve seen no coverage of it in the media whatsoever, no mention of it.”

Mr. Ballenger noted that the Peters campaign did bring up climate change last week in a press release, but it didn’t have much impact.

“The Peters people put out a press-release blast against Terri Land for allegedly making disparaging comments about climate change and being a denier and all that sort of thing,” Mr. Ballenger said. “But again, the Peters people have put out attack press releases on so many issues every day, for weeks, that it just kind of gets lost in the shuffle.”

Maine political analyst Phil Harriman said there has been little discussion of climate change in the governor’s race, where NextGen is backing Democratic Rep. Michael H. Michaud in his battle to unseat Republican Gov. Paul LePage.

“In terms of major talking points, climate change has not reached a pivotal discussion point. It’s not a campaign issue,” said Mr. Harriman, a former Republican state senator.

That climate change enthusiasm deficit is not for NextGen’s lack of trying.

The committee has run slews of television ads blasting Republicans for “denying the science of climate change,” but it still hasn’t cracked the polls as a hotbed issue. Climate change doesn’t appear on Gallup’s monthly list of “most important problem” list, and even the more general “environment/pollution” category gets only 2 percent of the total.

Perhaps as a result, even NextGen Climate isn’t focused solely on the climate. The committee also has sponsored commercials weighing in on standard Democratic Party talking points such as the Koch brothers and birth control aimed more at boosting Democrats than spreading the word on climate.

For example, NextGen’s fingerprints are on a radio ad airing in the Senate race in Colorado that accuses Republican Rep. Cory Gardner of banning condoms. On Monday, NextGen contributed $239,000 to the NARAL Pro-Choice Colorado IE Committee, which then paid a consultant for the radio ad, according to The Federalist.

The ad deals mainly with birth control, but inserted at the end is a salute to climate change. After griping that he can’t find condoms at any store, a man says to a woman, “Climate change that everyone knows is weirding our weather, Cory flat-out denies it. Sweet Pea, Cory denies science.”

NextGen Action Climate did not respond Wednesday to a request for comment.

Electing Democrats didn’t appear to be the primary goal when Mr. Steyer told The New York Times in May that he would raise $100 million to draw attention to climate change in this year’s election campaigns.

In fact, he originally hinted that he might target Sen. Mary L. Landrieu of Louisiana. The Democrat is a strong proponent of oil and gas development and the Keystone XL pipeline.

Since then, however, Mr. Steyer has been herded into the Democratic fold. He even gave $5 million to the Senate Majority PAC, which has helped fund Ms. Landrieu. NextGen also is funding an extensive ground game with hundreds of door-to-door field workers aimed at getting out the Democratic vote.

Democrats tend to be more alarmed about climate change than Republicans, but pushing the issue exclusively has drawbacks. In Colorado, for example, some voters view climate change activism as a threat to the state’s oil and gas industry and job creation.

At debates and forums, Democratic Sen. Mark Udall routinely says Mr. Gardner “doesn’t believe in climate change.” The Republican invariably counters that he believes the climate is changing but he disagrees about how much is caused by humans.

Of the seven Steyer candidates, Mr. Udall may have the strongest environmental credentials, but even his campaign isn’t trained on climate change. He is running the “war on women” playbook, and there is a reason for that, said Denver pollster Floyd Ciruli.

“It [climate change] does not appear to be moving the election in any significant way. It’s at the bottom of issues lists,” said Mr. Ciruli. “It’s really a niche issue. It appeals to a younger, more environmental demographic.”

In Maine, the issue is linked to the proliferation of windmill farms, which aren’t necessarily popular with voters.

“There are ads every day that Maine’s pristine environment is being imposed on and degraded by these windmills funded with taxpayer dollars,” Mr. Harriman said. “To inject climate change would not be effective.”

Another problem: The weather isn’t cooperating. Climate change activists often point to extremes in temperature as evidence that global warming is wreaking havoc, but the weather in most areas this year has been mild.

“If there were a series of really bad hurricanes — but we haven’t had that. Or if we had an extremely hot summer — but we had a cool spring, cool first part of the summer and warmer second part of the summer,” Mr. Smith said. “We haven’t had droughts, we haven’t had snowstorms, we haven’t had any adverse, climactic events that people might really pay attention to. So it’s not in people’s minds.”